1. Field of the Invention
This invention relates to rotating control devices to be used in the field of fluid drilling equipment.
2. Description of the Related Art
Conventional oilfield drilling typically uses hydrostatic pressure generated by the density of the drilling fluid or mud in the wellbore in addition to the pressure developed by pumping of the fluid to the borehole. However, some fluid reservoirs are considered economically undrillable with these conventional techniques. New and improved techniques, such as underbalanced drilling and managed pressure drilling, have been used successfully throughout the world. Managed pressure drilling is an adaptive drilling process used to more precisely control the annular pressure profile throughout the wellbore. The annular pressure profile is controlled in such a way that the well is either balanced at all times, or nearly balanced with low change in pressure. Underbalanced drilling is drilling with the hydrostatic head of the drilling fluid intentionally designed to be lower than the pressure of the formations being drilled. The hydrostatic head of the fluid may naturally be less than the formation pressure, or it can be induced.
These improved techniques present a need for pressure management devices, such as rotating control heads or devices (referred to as RCDs). RCDs, such as proposed in U.S. Pat. No. 5,662,181, have provided a dependable seal in the annular space between a rotating tubular and the casing or a marine riser for purposes of controlling the pressure or fluid flow to the surface while drilling operations are conducted. Typically, a member of the RCD is designed to rotate with the tubular along with an internal sealing element(s) or seal(s) enabled by bearings. The seal of the RCD permits the tubular to move axially and slidably through the RCD. As best shown in FIG. 3 of the '181 patent, the RCD has its bearings positioned above a lower sealing element or stripper rubber seal, and an upper sealing element or stripper rubber seal is positioned directly and completely above the bearings. The '181 patent proposes positioning the RCD with a housing with a lateral outlet or port with a circular cross section for drilling fluid returns. As shown in FIG. 3 of the '181 patent, the diameter of a circular flange at the end of a circular conduit communicating with the port is substantially smaller than the combined height of the RCD and housing. The term “tubular” as used herein means all forms of drill pipe, tubing, casing, riser, drill collars, liners, and other tubulars for drilling operations as are understood in the art.
U.S. Pat. No. 6,138,774 proposes a pressure housing assembly with a RCD and an adjustable constant pressure regulator positioned at the sea floor over the well head for drilling at least the initial portion of the well with only sea water, and without a marine riser. As shown in FIG. 6 of the '774 patent, the diameters of the circular flanges are substantially smaller than the combined height of the RCD and pressure housing. Also shown in FIG. 6 of the '774 patent, a lubrication unit pressurized by a spring loaded piston is proposed that is separated from but in fluid communication with a housing disposed with a sealed bearing assembly. It is proposed that lubricant may be injected into fissures at the top and bottom of the bearing assembly to lubricate the internal components of the bearing assembly.
U.S. Pat. No. 6,913,092 B2 proposes a seal housing with a RCD positioned above sea level on the upper section of a marine riser to facilitate a mechanically controlled pressurized system that is useful in underbalanced subsea drilling. A remote controlled external disconnect/connect clamp is proposed for hydraulically clamping the bearing and seal assembly of the RCD to the seal housing. As best shown in FIG. 3 of the '092 patent, in one embodiment, the seal housing of the RCD is proposed to contain two lateral conduits extending radially outward to respective T-connectors for the return pressurized drilling fluid flow. As further shown in FIG. 3 of the '092 patent, each diameter of the two lateral conduits extending radially outward are substantially smaller than the combined height of the RCD and seal housing.
U.S. Pat. No. 4,949,796 proposes a bearing assembly with a rotatable sealing element disposed with an assembly carrier. The assembly carrier is proposed to be removably attached with a stationary housing with a clamping assembly.
U.S. Pat. No. 7,159,669 B2 proposes that the RCD positioned with an internal housing member be self-lubricating. The RCD proposed is similar to the Weatherford-Williams Model 7875 RCD available from Weatherford International of Houston, Tex. The '669 patent proposes two pressure compensation mechanisms that maintain a desired lubricant pressure in the bearing assembly. One pressure compensation mechanism is proposed to be disposed directly and completely above the bearings, and the other pressure compensation mechanism is proposed to be disposed directly and completely below the bearings. Both pressure compensation mechanisms are proposed to be disposed directly and completely between the upper and lower rotatable seals.
U.S. Pat. No. 7,487,837 proposes a remotely actuated hydraulic piston latching assembly for latching and sealing a RCD with the upper section of a marine riser or a bell nipple positioned on the riser.
Pub. No. US 200610144622 A1 proposes a system and method for cooling a RCD while regulating the pressure on its upper radial seal. Gas, such as air, and liquid, such as oil, are alternatively proposed for use in a heat exchanger in the RCD.
An annular blowout preventer (BOP) has been often used in conventional hydrostatic pressure drilling. As proposed in U.S. Pat. No. 4,626,135, when the BOP's annular seals are closed upon the drill string tubular, fluid is diverted via a lateral outlet or port away from the drill floor. However, drilling must cease because movement of the drill string tubular will damage or destroy the non-rotatable annular seals. During normal operations the BOP's annular seals are open, and drilling mud and cuttings return to the rig through the annular space. For example, the Hydril Company of Houston, Tex. has offered the Compact GK® 7 1/16″—3000 and 5000 psi annular blowout preventers.
Small drilling rigs with short substructure heights have been used to drill shallow wells with conventional drilling techniques as described above. Some small land drilling rigs are even truck mounted. However, smaller drilling rigs and structures are generally not equipped for managed pressure and/or underbalanced drilling because they lack pressure containment or management capability. At the time many such rigs were developed and constructed, managed pressure and/or underbalanced drilling was not used. As a result of their limited substructure height, there is little space left for additional equipment, particularly if the rig already uses a BOP.
As a result of the shortage of drilling rigs created by the high demand for oil and gas, smaller drilling rigs and structures are being used to drill deeper wells. In some locations where such smaller rigs are used, such as in western Canada and parts of the northwestern and southeastern United States, there exist shallow pockets of H2S (sour gas), methane, and other dangerous gases that can escape to atmosphere immediately beneath the drill rig floor during drilling and/or workover operations. Several blowouts have occurred in drilling and/or workovers in such conditions. Even trace amounts of such escaping gases create health, safety, and environmental (HSE) hazards, as they are harmful to humans and detrimental to the environment. There are U.S. and Canadian regulatory restrictions on the maximum amount of exposure workers can have to such gases. For example, the Occupational Safety and Health Administration (OSHA) sets an eight hour daily limit for a worker's exposure to trace amounts of H2S gas when not wearing a gas mask.
Smaller drilling rigs and structures are also typically not able to drill with compressible fluids, such as air, mist, gas, or foam, because such fluids require pressure containment. There are numerous occasions in which it would be economically desirable for such smaller rigs to drill with compressible fluids. Also, HSE hazards could result without pressure containment, such as airborne debris, sharp sands, and toxins.
As discussed above, RCDs and their housings proposed in the prior art cannot fit on many smaller drilling rigs or structures due to the combined height of the RCDs and their housings, particularly if the rigs or structures already use a BOP. The RCD's height is a result in part of the RCD's bearings being positioned above the RCD's lower sealing element, the RCD's accommodation, when desired, for an upper sealing element, the means for changing the sealing element(s), the configurations of the housing, the area of the lateral outlet or port in the housing, the thickness of the bottom flange of the housing, and the allowances made for bolts or nuts on the mounting threaded rods positioned with the bottom flange of the housing.
RCDs have also been proposed in U.S. Pat. Nos. 3,128,614; 4,154,448; 4,208,056; 4,304,310; 4,361,185; 4,367,795; 4,441,551; 4,531,580; and 4,531,591. Each of the referenced patents proposes a conduit in communication with a housing port with the port diameter substantially smaller than the height of the respective combined RCD and its housing.
U.S. Pat. No. 4,531,580 proposes a RCD with a body including an upper outer member and a lower inner member. As shown in FIG. 2 of the '580 patent, a pair of bearing assemblies are located between the two members to allow rotation of the upper outer member about the lower inner member.
More recently, manufacturers such as Smith Services and Washington Rotating Control Heads, Inc. have offered their RDH 500® RCD and Series 1400 “SHORTY” rotating control head, respectively. Also, Weatherford International of Houston, Tex. has offered its Model 9000 that has a 500 psi working and static pressure with a 9 inch (22.9 cm) internal diameter of its bearing assembly. Furthermore, International Pub. No. WO 2006/088379 A1 proposes a centralization and running tool (CTR) having a rotary packing housing with a number of seals for radial movement to take up angular deviations of the drill stem. While each of the above referenced RCDs proposes a conduit communicating with a housing port with the port diameter substantially smaller than the height of the respective combined RCD and its housing, some of the references also propose a flange on one end of the conduit. The diameter of the proposed flange is also substantially smaller than the height of the respective combined RCD and its housing.
The above discussed U.S. Pat. Nos. 3,128,614; 4,154,448; 4,208,056; 4,304,310; 4,361,185; 4,367,795; 4,441,551; 4,531,580; 4,531,591; 4,626,135; 4,949,796; 5,662,181; 6,138,774; 6,913,092 B2; 7,159,669 B2; and 7,487,837; Pub. No. U.S. 2006/0144622 A1; and International Pub. No. WO 2006/088379 A1 are incorporated herein by reference for all purposes in their entirety. The '796, '181, '774, '092, '669 and '837 patents and the '622 patent publication have been assigned to the assignee of the present invention. The '614 patent is assigned on its face to Grant Oil Tool Company. The '310 patent is assigned on its face to Smith International, Inc. of Houston, Tex. The '580 patent is assigned on its face to Cameron Iron Works, Inc. of Houston, Tex. The '591 patent is assigned on its face to Washington Rotating Control Heads. The '135 patent is assigned on its face to the Hydril Company of Houston, Tex. The '379 publication is assigned on its face to AGR Subsea AS of Straume, Norway.
As discussed above, a long felt need exists for a low profile RCD (LP-RCD) system and method for managed pressure drilling and/or underbalanced drilling. It would be desirable to have a means for lubrication of the bearings of such a LP-RCD. It would be desirable to be able to efficiently replace the seal from the bearing assembly while leaving the bearing assembly in place. It would also be desirable to be able to efficiently remove the bearing assembly from its housing while leaving the housing in place.